A conventional intake control system for an internal combustion engine of this type is disclosed in PTL 1. This internal combustion engine is e.g. a diesel engine, including an intake throttle valve that is disposed in an intake passage, an EGR passage that is connected to an exhaust passage and a portion of the intake passage downstream of the intake throttle valve, for recirculating part of exhaust gases discharged into the exhaust passage, and an EGR valve that is disposed in the vicinity of an outlet of the EGR passage to the intake passage, for adjusting the EGR amount.
Further, in this intake control system, a differential pressure across the EGR valve is calculated, and if the calculated across-valve differential pressure is not more than a predetermined value, the intake throttle valve is throttled to thereby increase the across-valve differential pressure. As a consequence, the differential pressure across the EGR valve is ensured, and a degree of change in EGR amount with respect to an opening degree of the EGR valve is made moderate to thereby perform control of the EGR amount by the EGR valve with high accuracy.